Buildings having metal roof structures typically comprise a series of parallel rafter beams which are supported by vertical columns extending from the floor of the building. A plurality of spaced apart purlin beams extend in a direction normal to the rafter beams and are fastened to top portions of the rafter beams. Typically, the roofs generally have two sloped sections, each extending from a side of the building to a peak. To enclose the roof structure, sheets of hard roofing material, such as metal deck sheets can be used to cover the roof structure. The deck sheets are typically interlaced and fastened to the purlins.
Ordinarily, the roof structures include some type of insulation material placed above or below the deck sheets to provide thermal insulation for the building. In one type of insulated roof structure, insulation material in long sheets is placed in the area between purlins. The sheets of insulation material can be laid along the length of the purlins or across the purlins in a direction normal to the purlins. The insulation material is supported between the purlins beneath the hard roofing material. Various methods of supporting the insulation material have been used. Mounting straps or wire mesh which are attached to or draped over the purlins forming a lattice have been used. A sheet, typically made of vinyl and acting as a vapor barrier, is then rolled onto the lattice, and insulation material is placed between adjacent purlins and over the sheet. Some systems dispense with the lattice and use the sheet itself to support the insulation material. The support sheet is dispensed from a roll and draped from adjacent purlins. Insulation material is then placed on top of the support sheet. A carriage has been used to aid in the dispensing of the support sheet, such as that disclosed in U.S. Pat. No. 4,967,535 to Alderman. The carriage is positioned on top of the purlins and travels the length of the purlins during the roof construction. A roll of the support sheet material is mounted on the carriage and the support sheet is dispensed from the roll and placed on top of the purlins. As the carriage travels the length of the purlins, the support sheet is draped across the purlins.
In another type of insulated roof structure, insulation material, such as rigid insulation board, is placed on top of metal deck sheets. The insulated board and the deck sheets are then fastened to the top portions of the purlins. A water proof membrane is then applied on top of the insulation board, to provide a weather tight seal.
It is customary to construct the roof along the length of the structure from one end to the other. The workers stand on the previously completed section of roof to construct the next section. Because the metal deck sheets typically comes in long sheets and the roofs generally have two sloped sections, it is customary to construct the roof along the length of the structure from one end to the other.
Of considerable importance to the construction of roof structures, is the safety of the workers. In the past, permanent netting has been provided under the workers on top of the roof structure to help prevent the workers from falling and from being hit by dropped objects, such as tools and bolts. U.S. Pat. No. 5,251,415 to Van Auken et al. discloses such a netting. Prior to construction of the roof, the netting is placed over the tops of the purlins. The netting spans the entire roof and can be placed in a loose manner to support insulation material placed on top to provide space for the insulation material. When the insulation material and the deck sheets are installed above the netting, the netting becomes a permanent structure of the roof. Although the use of this netting has been satisfactory, it can be difficult and time consuming to install the netting across the entire roof, since the netting must be attached around its periphery to the edges of the roof structure. Thus, workers are required to climb the building structure or be lifted to each attachment point to secure the netting.
For roof structures which are built using the carriage as described above, it has been known to provide a platform which extends from the carriage in a direction towards the completed section of the roof, such as that disclosed in U.S. Pat. No. 5,664,740 to Alderman et al. The platform extends underneath the top portions of the purlins and supports the support sheet as the support sheet is loosely draped between adjacent purlins. The platform can be built of sufficient strength so as to support a worker stepping or falling onto the platform. However, the roof structures often include purlin support bracing and straps which extend between adjacent purlins. To accommodate the bracing, the platform is positioned near the top of the purlins so that the platform will not be obstructed by the bracing as the carriage moves. Thus, the support sheet is relatively flat across the tops of the purlins and does not hang down into the space between the purlins. Insulation material placed on top of the support sheet is then compressed when the hard roofing material is attached to the purlins.
It would be desirable to have a system of building roof structures which is simple and less time consuming to use, and which provides adequate protection from falling objects and for the workers constructing the roof.